Field of the Invention
This invention concerns an improved process for preparing acetic acid and propionic acid and their esters by reaction of oxides of carbon with hydrogen in presence of a catalyst system.
There are ever-increasing efforts to provide new methods of making carboxylic acids such as acetic acid and esters thereof which are particularly useful in preparing a wide variety of organic compounds such as cellulose acetate, vinyl acetate etc. An ever present aim is to prepare such materials in relatively high yields directly from carbon monoxide and hydrogen utilizing a catalyst system providing good selectivity.
A number of processes have been described in the literature for manufacturing carboxylic acids and esters from carbon monoxide and alcohols or from carbon monoxide and hydrogen. For example, in U.S. Pat. No. 3,717,670 a method for preparing such carboxylic acids is disclosed in which an alcohol and carbon monoxide are reacted in the presence of a catalyst composition consisting of a rhodium compound and for example chromium trioxide. When hydrogen and carbon monoxide are passed over a catalyst comprising rhodium in combination with tungsten a reaction product containing acetic acid, acetaldehyde and/or ethanol is formed according to the disclosure of U.S. Pat. No. 4,096,164. A similar method is described in U.S. Pat. No. 4,014,913 where carbon monoxide and hydrogen are reacted in the presence of a rhodium-manganese catalyst. The reaction of carbon monoxide and hydrogen in the presence of a rhodium metal catalyst to give a liquid product containing a substantial proportion of acetic acid, ethanol and/or acetaldehyde is disclosed in U.S. Pat. No. 4,246,186. Likewise in U.S. Pat. No. 4,162,262 it is noted that the reaction of hydrogen and carbon monoxide in the presence of a catalyst comprising thorium and/or uranium yields a product containing a large amount of two-carbon atom products.
One of the problems associated with the above-described processes is that a wide variety of liquid organic products are formed also, generally the yield of carboxylic acids and esters is low. There is a definite need in the art therefore for a process which will give a high yield of the desired carboxylic acids and especially acetic acid and esters thereof.